Long term evolution (Long Term Evolution, LTE) is the biggest new technology research and development project that has been launched in the recent two years by the 3rd generation partnership project (3rd Generation Partnership Project, 3GPP), and may be regarded as a “quasi-4G” technology. The LTE improves and enhances an air access technology of 3G, and adopts orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) and multiple user equipment multiple input multiple output (Multiple Input Multiple Output, MIMO) as a basic technology for its wireless network evolution.
An LTE single-card dual-standby multi-mode terminal, for example, an LTE+2G/3G single-card dual-standby multi-mode terminal, resides in two communication subsystems at the same time, in which a circuit switched domain (Circuit Switched Domain, CS domain) resides in a 2G/3G system, and a packet switched domain (Packet Switched Domain, PS domain) resides in an LTE system. The LTE+2G/3G single-card dual-standby multi-mode terminal may perform a PS service in the LTE system and perform a CS service in the 2G/3G system at the same time through the two communication subsystems. Quality of a voice service of the LTE+2G/3G single-card dual-standby multi-mode terminal is consistent with quality of a voice service of a 2G/3G terminal, which avoids various defects caused by a CS Fallback (Circuit Switched Fallback) solution of a LTE terminal at present, such as time delay increase, handover failure, and system modification.
Both of the two communication subsystems (the LTE system and the 2G/3G system) of the LTE single-card dual-standby multi-mode terminal are both in a working state when the CS service and the PS service are concurrent. Radio frequencies of the two communication subsystems may receive and transmit wireless signals, and therefore mutual interference exists, that is, a transmitter in one mode affects sensitivity of a receiver in another mode. A mutual interference level of the LTE single-card dual-standby multi-mode terminal has a close relationship with transmit power and an interval between two frequency bands working at the same time. The mutual interference is larger in a case that the transmit power is larger, a distance between two antennas is shorter, and the interval between the frequency bands is smaller (for example, a frequency band of 1880-1920 MHz of the LTE/3G and a frequency band of 1805-1880 MHz of 2G). In the prior art, filters are used in sending and receiving directions of a radio frequency to reduce the interference. If the interference is large, a high-performance filter with better out-of-band attenuation characteristics may be considered for use.
However, a problem of the mutual interference of the LTE single-card dual-standby multi-mode terminal cannot be completely solved by using the filters in the prior art. Especially when two working radio frequency bands are close to each other, and a spatial distance between the antennas is close, a target value of the interference cannot be reduced even when the high-performance filter is used, and the cost of the terminal may be increased due to the use of the filters.